A network operator may be required in certain instances to intercept and provide access to Content of Communications (CC) and Intercept Related Information (IRI) related to a target. For example, Law Enforcement Agencies (LEAs) may submit an intercept request (e.g., lawful authorization or warrant), which specifies at least the target, the type of intercept (i.e., IRI-only or IRI and CC), the authorized period of interception, and the address to which intercepted information is to be delivered. The request may include other interception parameters.
Upon receiving such a request, the network operator (in some documents named the communication service provider), intercepts and forwards the requested information in association with a Communication Identity Number (CIN) that uniquely identifies an intercepted communication session. Details of lawful interception are described in various standards, such as ETSI TS 102 232 related to “Lawful Interception (LI); Handover Interface and Service-Specific Details (SSD)” (more specific: version 3.2.1 of part 5 and version 3.6.1 of part 1) or ETSI TS 101 671, “Lawful Interception; Handover Interface for the lawful interception of telecommunication traffic” version 3.12.1.
Most existing handover interfaces use CIN. However, in networks providing voice over packet (VoP) services, maintaining a unique CIN becomes difficult because there are usually several nodes involved in signaling (e.g., SIP proxies). A Mediation Function (MF) tries to correlate different signaling messages coming from different nodes in order to use the same CIN for the same communication session. However, conventional algorithms are unable to maintain the same CIN for all results of the interception when call forwarding (e.g., Call Forwarding Unconditional, CFU, Call Forwarding on Busy, CFB, or Call Forwarding on No-Reply, CFNR) occurs during a session. The forwarded call is then treated as a new session with a new CIN.
Therefore, it is desirable for network operators to be able to relate an initial call and the redirected (i.e., forwarded) call to maintain the same CIN for a communication session during which forwarding occurs.